The provision of high purity gas streams is critically important in a wide variety of industrial and research applications. The rapid expansion of vapor-phase processing techniques, e.g. chemical vapor deposition, in the semiconductor industry has been associated with the deployment and use of manufacturing equipment that is totally reliant on the delivery of ultra-high purity process gases at the point of use in the semiconductor manufacturing facility.
Considering the impurities which are present in gas streams involved in semiconductor manufacturing, it is to be noted that the growth of high quality thin film electronic and optoelectronic cells by chemical vapor deposition or other deposition techniques is inhibited by a variety of low-level process impurities. These impurities can cause defects that reduce yields by increasing the number of rejects, which can be very expensive. These impurities may be particulate or chemical contaminants.
Chemical impurities may originate in the production of the source gas itself, as well as in its subsequent packaging, shipment, storage, and handling. Although manufacturers typically provide analyses of source gas materials delivered to the semiconductor manufacturing facility, the purity of the gases may change because of cross contamination or from contamination arising from improperly prepared containers, e.g. gas cylinders, in which the gases are packaged. Impurity contamination may also result from improper gas cylinder changes, leaks into downstream processing equipment, or unexpected contamination arising from such downstream equipment.
In numerous industrial and commercial processes, it may be desirable to provide high purity germane. One area in which high purity germane is typically required is in the fabrication of semiconductor devices such as transistors, diodes, integrated circuits, detectors, solar cells, and the like. In many of these applications, high purity germane is oftentimes used as a gas for deposition of silicon-germanium alloys or for doping of substrates. More recently, the commercial use of germanium tetrahydride by the semiconductor and solar cell manufacturers has steadily increased because of new technology that incorporates germanium into active silicon structures. This new technology requires that germane be produced at higher purity levels with less variability in impurity concentration.
Germane may contain a phosphine contaminate due to unexpected variation in raw materials, unexpected manufacturing process conditions or unexpected container related conditions. Separation of two molecules such as germane and phosphine of similar volatility and relatively similar molecular weight thereby reducing the unwanted material down to low, less than 50 ppb, levels has not been reported in the literature.